Rudimentary Linux Support.

This patch adds a couple of hacks to enable Insane Limits to be run on Linux using Mono. Currently some manual intervention is needed to get it working right (such as adding a `/` to the start of the path in the `limits_file` property in PRoCon, and manually inserting your limits configurations as it may overwrite them), however it does enable the plugin to save settings and compile Limits.

Tested on a vanilla (no other plugins) PRoCon setup with Ubuntu 12.04 x86 with Mono 2.10.8.1

```
Mono JIT compiler version 2.10.8.1 (Debian 2.10.8.1-1ubuntu2.2)
Copyright (C) 2002-2011 Novell, Inc, Xamarin, Inc and Contributors. www.mono-project.com
        TLS:           __thread
        SIGSEGV:       altstack
        Notifications: epoll
        Architecture:  x86
        Disabled:      none
        Misc:          softdebug
        LLVM:          supported, not enabled.
        GC:            Included Boehm (with typed GC and Parallel Mark)
```